Iductor-dynamo



UNITED TATES PATENT @FFTCE.

CHARLES P. STEINMETZ, OF SCHENECTADY, NEWV YORK, ASSIGNOR TO THE GENERALELECTRIC COMPANY, OF NEW YORK.

lNDUCTOR-DYNAMO.

SPECIFICATION forming part of Letters Patent No. 594,145, dated November23, 1897. Application filed August 12, 1897. Serial No. 647,963. (Nomodel.)

To all whom it may concern: of a slot. Thus the magnetism in the latterBe it known that I, CHARLES P. STEINMETZ, case tends to decrease, andthis induces eddya citizen of the United States, residing at currents inthe whole magnetic structure. Schenectady, in the county of Schenectady,The use of the short-circuited winding, for 5 State of New York, haveinvented certain reasons more fully to be pointed out, tends new anduseful Improvements in Inductorto obviate this difliculty. Dynamos,(Case No. 589,) of which the follow- The accompanying drawings show amaing is a specification. chine constructed according to my invention,

My invention relates to alternating-current it being applied to a dynamoof the well-known IO dynamos of the inductor type, and has for itsThomson induct-or alternator type; but it object to remedy some of thedifficulties which might equally well be applied to any other have beenmet with in designing satisfactory machine of the same general class.machines of this class. In inductor-dynamos Figure 1 is an endelevation, partly in secthe armature and field-magnet coils are station,of such a machine; and Fig. 2 is a side I 5 tionary and the induction isproduced by a elevation,partly broken away for convenience change in thepath of the magnetic flux efof illustration. fected by the teeth orpoles of the rotating In Fig. 1, A is the yoke or external portioninductor. In consequence in part of the magof the armature-core. B isthe inductor, connetic circuit the magnetism varies, and this sisting ofthe usual yoke F and the laminated 20 part, to avoid eddy-currents, mustbe laminateeth I) b. C C are the armature-teeth, conted, while in theother parts the magnetism is sisting, as is usual in such machines, oflamistationary and solid material may be used. nated iron, the yokeEbeing ordinarily made It is therefore of importance to avoid changes ofcast-iron or mild steel. Surrounding the in magnetism in the solid partof the strucinductor and supported by the yoke are the 25 ture in orderto avoid excessive heating and field-magnet coils E E, they being, as iswell loss from eddy-currents. understood, stationary. In themachineillus- During the rotation of the inductor the trated each of thearmature-teeth is surlength of the path of the lines of magnetic roundedwith a single coil D, but this is force, and thereby the reluctance,varies pemerely typical of any selected type or con- 3o riodically inthe laminated portion of the arnection of winding. G is the auxiliaryairmature, which tends to make the magnetic gap to which Ihave referredin my statement density vary periodically also. To keep this ofinvention, separating the laminated armaperiodic variation of magneticdensity from ture-iron from the yoke E. Between the yoke extending intothe solid part of the magnetic F of the inductor and the supporting-yokeE 3g circuit, I insert an auxiliary air-gap between of the armature isthe air-gap K, and the the solid and the laminated part of sufficientusual air-gap e is also located between the length to make the magneticreluctance of the inductor and. the armature. The action of shortest andof the longest path across the this part of my invention will be bestunderarmature-iron and auxiliary air-gap practistood from Fig. 2. Themagnetic lines en- 4o cally equal, and thus the magnetic density teringfrom the tooth h in the upper part of at the point of entrance into thesolid part of the figure and threading the coil spread out the magneticcircuit practically uniform. in both directions in the iron of the arma-Another feature of my invention consists ture, reaching the yoke E atthe point .9 in a in the use, in an inductor-dynamo, of ashortpractically straight line from the tooth and 5 5 circuited orsquirrel-cage winding surroundat the point 25 over the path 2 which iscurved ing the outer edge of the armature-iron. The and is considerablylonger than the path 00, magnetic reluctance of the air-gap betweenhaving, therefore, higher magnetic relucthe inductor and the armature,especially in tance. The magnetic density at s will be unitoothedsinglephase machines, is less greater than at t. By the rotation of thein- I00 50 when the inductor-tooth stands in front of an ductor at thenext moment the inductor-tooth armature-tooth than when it stands infront 12 will stand in front of the next tooth of the armature, and thepath to the point t will be approximately straight, while that to thepoint 5 will be curved, and thus higher density will exist at the point'6 than at the point 3. To avoid these pulsations of magnetism in theyoke E is the object of the air-gap G. The reluctance of this gap beingvery large as compared with the reluctance of the armature-iron (aspointed out in the statement of invention) makes the total reluctance ofthe path y practically equal to the reluctance of the path or, andthereby insures practically a uniform distribution of magnetism in theyoke.

To assist the effect to which I have referred, I also provide ashort-cireuitcd squirrel-cage winding consisting of the copper pins I,Figs. 1 and 2, which pass through the iron of the armature near itsouter edge and are connected upon each side of the iron by theshortcircuiting bands II, also of lowresistance metal. Any pulsation orvariation of the magnetic flux reaching the outside of the armature actsto induce secondary currents in this short-circuited win ding. Thesecurrents tend to magnetize at the points of lower 1n agnetic density andto demagnctize at the points of higher density, and thus cause a uniformdistribution of the magnetic flux at the outer part of the armaturethatis, when the flux enters the solid structure. The action of this windingis also beneficial in causing uniform distribution of magnetism and inpreventing pulsation of the magnetism in the entire magnetic circuit dueto the differences of reluctance in the main air-gap of the machinecaused by the revolution of the inductor. As

already pointed out, the reluctance is less when the inductor-teethstand in front of the armature-teeth and greater when theystand in frontof a slot, thus giving rise to changes in the distribution of the fluxand inducing eddy-currents in the whole structure.

It has been proposed to remedy this to some extent by Winding thefield-magnet coils E upon a solid copper ring or spool. While this isuse ful, the construction which I have indicated acts in a moreefficient manner because it influences directly the armature-iron of thema chine.

I'Vhat I claim as new, and desire to secure by Letters Patent of theUnited States, is-

1. An inductor-dynamo, comprising a revolving inductor and a stationaryarmature, the latter having portions of laminated iron and a solid yoke,with an auxiliary or additional air-gap in the armature-iron.

2. An inductor-dynamo having a revolving inductor and stationaryarmature, the armature having on its outer edge a short-eircuited orsquirrel-cage Windin g.

S. An inductor-dynamo, comprising a rcvolving inductor and a stationaryarmature, the armature provided with. an auxiliary airgap in its circuitand a short-circuitcd or squirrel-cage winding near its outer edge.

t. In a dynamo, an auxiliaryor additional air-gap between the laminatedand the solid parts of the magnetic circuit.

5. In an inductor-dynamo, an air-gap between the laminated and solidparts of the armature-iron.

6. In a dynamo-electric machine of the in ductor type, the combinationof a polar inductor, and an annular magnetic structure recessed toreceive the armature-coils and having its magnetic reluctance increasedby an air gap or gaps, of high reluctance compared with the reluctanceof the armatureiron.

In witness whereof I have hereunto set my hand this 10th day of August,1897.

CHARLES l. 5"]fllltllllfll7l. Witnesses:

B. 1;. HULL, A. ll'. ABET/L.

